Electric furnace.



H. 1. 001). ELEGTRIG FURNACE. APPLICATION FILED JULY2, 1906 Patented Feb. 14, 1911.-

5 WHY 5 E N w INVENTDR. HElWA RD I Wanna.

UNITED OFFICE.

HOWARD WOOD, OF SCHENECTADY, NEW'YORK, ASSIGNOR TC GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC FURNACE.

Specification of Letters Patent.

Application filed July 2, 190B.

Patented Feb. 14, 1 911.

Serial No. 324,388.

To all whom it may concern:

Be it known that I. Ilowxno I. Voon, a citizen of the United States. residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a speciieation.

Several of the refractory metals are known to have a fusing temperature higher than that at which carbon or graphite ap pears to vaporize and disintegrate in mono, and various reducible compounds of these metals require for reduction :1 temperature higher than can be produced by a resistance conductor of graphite without danger that the product will be contaminated by carbon given oil by the heating member.

My invention comprises means for. the protection of the material under treatment from any substantial contamination by carprevent its action on the charge within the hon, even though the material under treatment may be heated in the presence of graphite to a temperature considerably higher than that at which graphite begins to isintegrate.

The drawing is a sectional elevation of one type of furnace to which my invention may -e applied.

The furnace consists of a water cooled metal envelop 1 having airdight joints and an outlet 2 for connection with a vacuum pump. The pump is used for exhausting the chamber and for insuring a low pressure at all stages of the heat treatment. The resistance conductor of the furnace consists of a helix 3 of graphite, clamped at the top to a U-shaped tube 4, which passes through the to of the chamber and serves as a means for do ivering current to the refractory helix. The tube may be supplied with a cooling liquid to insurea goo contact at the end of the helix and to prevent vaporization of the metal clamps 5 by means of which the helix is clamped to the tube. A similar U-shaped tube 6 is clamped to the lower end of the helix and serves as a support therefor and as means for connecting to a source of power. The material 7 to be treated is inclosed in a covered crucible 8 Within the refractory helix but out. of contact therewith. To in sure a concentration of heat on the crucible and its contents, the helix is surrounded hr a refractory shield 9 consisting of an annuchamber formed by envelop 1 has been evacuated. current is passed through the refractory helix 3 and the charge is heated up to the desired temperature. 7 If the desired temperature is higher than that at which carbon disintegrates, there is danger that the material of the helix or of the surrounding shield will pass into the charge and change the chen'iical composition thereof. I find, however, that by making the crucible of suitable material I can protect the charge from the -arbon,- even at exceedingly high temperatures. If the charge is of tantalum oxid, I may make the crucible of tantalum oxid or of tantalum carbid. as these mate rials will absorb the. vaporized carbon and crucible. If the charge is metallic tantalum which is to be melted or fused, I may make the. crucible of tantalum carbid.

I have referred to tantalum and its oxid as material suitable for treatment in this furmice but I desire it to be understood that I may treat" other refractory metals or their compounds to fuse the materials or to reduce or otherwise modify the compounds. All this may be done at a temperature higher than that at which carbon disin tegrates, by surrounding the material under treatment with a crucible or other envelop consisting of material which does not react on the charge and which has sufficient power of absorbing carbon vapors to prevent any substantial contamination of the charge by carbon given off by the heating members of the furnace.

Although I may treat other materials than tantalum and use other protective material than tantalum oxid, I consider that these are typical of the general class of inaterials to which my invention applies and will serve to disclose my invention to persons skilled in the art.

\Vhat I claim as new amldesireto secure by Letters Patent of the United States,is,

1. The combination of an evacuated chamher, a tubular resistance heater of carbonaceous material, within said chamber, means for supporting a charge in proximityto said heater, and a closed envelop withinevacuated chamber, a graphite resistance heater within said envelop subject. to disintegration when in normal opcrat'iom-and a closed envelop inclosing the furnace charge and separated from said heater by an evacuated space, said charge-inclosiug envelop consisting of: material capable of chemically uniting with such carbon vapor as crosses said space.

3. In a furnace, the combination of an evacuated chamber, a tubular resistance heater within said chamber subject to disintegration by heat at normal operating temperature of the furnace, and-a charge protecting envelop within said heater and separated therefrom by an annular gap, said envelop consisting oi: material capable of uniting with material liberated by said heater. 7 4

4. The combination of an evacuated chamher, a heater of carbonaceous material there- 30 envelop consisting of a refractory compound of a refractory metal, said compound having high afiinity for carbon.

5. The combination of an evacuated chamher, a resistance heater therein consisting of carbonaceous material, and a. closed chargeinelosing envelop in proximity therewith having a marked atlinity for carbon and yielding a reduction product stable at the ten'iperature at. which carbon begins to lisintegrate.

(3. The combination of a resistance heater, and a charge protecting envelop proximity thereto but out o'l. contact therewith having high atlinity for the material of said heater and yielding a stable product when associated with vaporized material from said heater.

7. The combination of an cvacuatettenvelop, a hollow resistance heater therein ot' carbonaceous material, and a closed chargeproteoting envelop'iu proximity thereto but. out. of contact therewith, having a high atlinity for carbon.

ln wituess vhercot, I. ha re hereunto set. m hand this 30th day of June, 1906.

HOWARD I. WOOD.

l-Vitnesses:

Enwaun \VILLIAMS, Jr.., Alma. B. MARVIN, Jr. 

